BC break: Renamed plugin configuration setting ini_file
to config_file. In early versions the plugin configuration
file used ini style. Back then the configuration setting was named accordingly.
It has now been renamed to reflect the newer file format and to distinguish it
from PHP's own ini file (configuration directives file).

Introduced new default charset setting server_charset
to allow proper escaping before a connection
is opened. This is most useful when using lazy connections, which are a default.

Introduced wait_for_gtid_timeout setting to throttle
slave reads that need session consistency. If global transaction identifier are
used and the service level is set to session consistency, the plugin
tries to find up-to-date slaves. The slave status check is done by
a SQL statement. If nothing else is set, the slave status is checked only
one can the search for more up-to-date slaves continues immediately
thereafter. Setting wait_for_gtid_timeout instructs the plugin
to poll a slaves status for wait_for_gtid_timeout seconds
if the first execution of the SQL statement has shown that the slave is not
up-to-date yet. The poll will be done once per second. This way, the plugin
will wait for slaves to catch up and throttle the client.

New failover strategy loop_before_master.
By default the plugin does no failover. It is possible to enable
automatic failover if a connection attempt fails. Upto version 1.3
only master strategy existed to failover to a master if
a slave connection fails. loop_before_master is
similar but tries all other slaves before attempting to connect to the master
if a slave connection fails.

The number of attempts can be limited using the max_retries option.
Failed hosts can be remembered and skipped in load balancing for the rest of
the web request. max_retries and
remember_failed are considered experimental although
decent stability is given. Syntax and semantics may change in the future
without prior notice.